1. Technical Field to Which the Invention Belongs
The present invention relates to a color conversion method and a color conversion apparatus in which a color signal outputted by hardware is converted into a color signal corresponding to a predetermined color space.
2. Prior Art
In hardware which outputs a color image signal utilizing a CCD (Charge Coupled Device), a CMOS (Complementary Metal Oxide Semiconductor) device, or the like, a method employing a lookup table (hereinbelow, abbreviated to “LUT”) for color conversion and a method employing a color conversion matrix for color conversion have heretofore been known in correcting an outputted color into an appropriate color.
Here, the method employing the LUT for the color conversion is capable of accurate color corrections, but it requires a large capacity memory for color conversion processing, so that it is difficult to be used in an apparatus, such as image input sensor, which cannot have a large capacity memory. Besides, when it is intended to curtail the LUT, arithmetic processing becomes complicated.
On the other hand, the method employing the color conversion matrix for the color conversion can convert the color at high speed without requiring a large capacity memory, and hence, it is usable even in an apparatus such as an image input sensor.
As the color conversion method employing the color conversion matrix, a technique wherein the color conversion matrix is mechanically calculated by a predetermined method and wherein an inputted color signal is converted into a color signal suited to a predetermined color space, by employing the generated color conversion matrix, is disclosed in, for example, Japanese Patent Application Laid-Open No. 3-16383 and No. 3-252268.
In the prior-art color conversion method employing the color conversion matrix, however, noise developed by the CCD or the like, and the influence of an illuminating light source are not taken into consideration. Therefore, a situation where appropriate color conversion cannot be effected occurs in a case where noise has been developed or where the illuminating light source has changed.
An object of the present invention is to easily convert a color by the use of a color conversion matrix which is capable of more appropriate color conversion.